The present invention relates to a base station apparatus and a mobile radio terminal used for a radio communication system, a radio communication system and a communicating method used in a radio communication system, which are suitable for use when a radio data communication network is configured with a mobile radio terminal station in a radio communication system.
In the case of data communication such as personal computer communication, plural personal computers or the like are heretofore connected to a telephone line via modems to communicate with each other.
When a data communication network is configured with mobile radio terminal stations accommodated in a communication network for the purpose of data communication, a personal computer or the like is generally connected to a mobile radio terminal via a modem.
FIG. 18 is a block diagram showing a radio communication system in the case where a data communication network is configured with PHSs (Personal Handyphone Systems) as the above mobile radio terminals. In FIG. 18, reference numerals 201 and 207 denote personal computers (PCs). These personal computers 201 and 207 are able to output data information at a transmission speed of, for example, 1200 bps.
Reference numeral 202 denotes a modem. The modem 202 functions as an interface between the personal computer 201 and a PHS terminal (a PS apparatus for PHS) 203.
More specifically, the modem 202 converts received signals (analog signals) from the PHS terminal 203 into digital signals at 1200 bps and transfers them to the personal computer 201, or converts transmission signals (digital signals at 1200 bps) from the personal computer 201 into analog signals and transfers them to the PHS terminal 203.
Further, reference numeral 206 denotes also a modem. The modem 206 functions as an interface between the personal computer 207 and a switching system 205.
More specifically, the modem 206 converts received signals (analog signals) from the switching system 205 into digital signals at 1200 bps and transfers them to the personal computer 207, or converts transmission signals (digital signals at 1200 bps) from the personal computer 207 and transfers them to the switching system 205.
The PHS terminal 203 is accommodated in a PHS base station 204 described later via a radio line 208, and has a function as a terminal being capable of implementing normal voice communication. On the other hand, when used for data communication by the personal computer 201, the PHS terminal 203 transmits and receives data signal information by analog signals to and from the modem 202.
The PHS terminal 203 has, in detail, an amplifying unit 203a, a PCM (PCM, Pulse-Code Modulation) processing unit 203b, an ADPCM (ADPCM, Adaptive Differential Pulse-Code Modulation) processing unit 203c and a transmitting/receiving unit (RF) 203d. These will be described below, focused on their functions used upon data communication.
The amplifying unit 203a amplifies analog signals from the modem 202 and outputs them, besides amplifying analog signals from the PCM processing unit 203b.
If the PHS terminal 203 functions as a terminal being capable of implementing normal voice communication, the amplifying unit 203a amplifies transmission analog voice signals inputted through a microphone not shown, besides regenerating voice data from a speaker not shown by amplifying received analog voice signals.
The PCM processing unit 203b converts PCM coded signals at a transmission speed of 64 kbps into analog signals which should be outputted to the modem 202, or converts analog signals from the modem 202 into PCM coded signals at a transmission speed of 64 kbps.
The ADPCM processing unit 203c compresses PCM coded signals at a transmission speed of 64 kbps from the PCM processing unit 203b into signals at a transmission speed of 32 kbps in synchronization with the radio line 208, or expands signals at a transmission speed of 32 kbps from the transmitting/receiving unit 203d into signals at 64 kbps.
The transmitting/receiving unit 203d is inputted thereto signals that should be transmitted to the PHS base station 204 over the radio line 208 from the ADPCM processing unit 203c, conducts, for example, a modulating process, a frequency converting process, an amplifying process and the like on the signals that should be transmitted and transmits them, besides conducting, for example, an amplifying process, a frequency converting process, a demodulating process and the like on signals received from the PHS base station 204 over the radio line 208 and outputting them to the ADPCM processing unit 203c.
The PHS base station (a CS apparatus for PHS) 204 exchanges signals as digital signals at 64 kbps with the switching system 205, besides exchanging signals as radio signals at 32 kbps with the PHS terminal 203.
To be concrete, the PHS base station 204 is connected to a line of, for example, four channels (at a transmission speed of, for example, 64 kbps) between the PHS base station 204 and the switching system 205. On the other hand, the PHS base station 204 communicates (in normal voice communication or communication using data signals) with the PHS terminal 203 over a radio line (at a transmission speed of, for example, 32 kbps) 208 using signals obtained by conducting a time-division multiplexing process on line signals on four channels.
As to the above signals on four channels, three channels are used as communication channels for transmitting and receiving communication signals to and from each PHS terminal 203, and the remaining one channel is used as a control channel for transmitting and receiving control signals to and from the switching system 32, for example.
The PHS base station 204 has, in detail, a transmitting/receiving unit 204a, a time division multiplexing/demultiplexing unit (TDMA-TDD, Time Division Multiple Access-Time Division Demultiple) 204b, an ADPCM unit 204c and an interface unit 204d.
The transmitting/receiving unit 204a is inputted thereto signals that should be transmitted to the PHS terminal 203 over the radio line 208 from a timedivision multiplexing/demultiplexing unit 204b, conducts a modulating process, a frequency converting process and an amplifying process on the signals that should be transmitted and sends them out, besides amplifying signals received from the PHS terminal 203 over the radio line 208, down-converting the signals and outputting them to the time-division multiplexing/demultiplexng unit 204b.
The time-division multiplexing/demultiplexing unit 204b demultiplexes signals having been multiplexed in a time-division fashion into, for example, four slots so as to convert them into signals at 32 kbps on four channels, and outputs them to the ADPCM unit 204c, besides outputting signals at 32 kbps on four channels from the ADPCM unit 204c in a frame format multiplexed in a time-division fashion to the transmitting/receiving unit 204a.
The ADPCM processing unit 204c compresses signals on four channels at 64 kbps from the switching system 205 into signals at 32 kbps in synchronization with the radio line 208, besides expanding frame signals from the time-division multiplexing/demultiplexing unit 204b into signals at 64 kbps in synchronization with a ground network.
The interface unit 204d has a function as an interface with the switching system 205 side.
The switching system 205 exchanges data information or voice data from the personal computers 201 and 207. In detail, the switching system 205 has a switching unit 205a and a PCM processing unit (PCM, Pulse-Code Modulation) 205b.
The PCM processing unit 205b converts PCM coded signals at a transmission speed of 64 kbps into analog signals that should be outputted to the modem 206, or converts analog signals from the modem 206 into PCM coded signals at a transmission speed of 64 kbps.
On the radio line 208, as shown in FIG. 19, for example, one communication channel is so assigned that up data (data from the PHS terminal 203 to the PHS base station 204) 208a and down data (data from the PHS base station 204 to the PHS terminal 203) 208b of one slot (160 bits) may be transmitted per 5 msec, whereby signals (voice data in the event of normal voice communication or data signals at the time of data communication such as personal computer communication or the like) may be transmitted as data at 32 kbps when they are transmitted over the radio line 208.
In other words, one slot of up line signals and down line signals is assigned per 5 msec, thereby establishing a path for an adaptive differential pulse code modulation at a transmission speed of 32 kbps.
As indicated by dotted line in FIG. 19, data on the remaining three channels are so assigned that the up data and down data of one slot may be transmitted per 5 msec.
Further, up data 208c and down data 208d on a control channel among the above four channels are intermittently transmitted per, for example, 100 msec as compared with the minimum transmitting/receiving cycle (5 msec), as shown in FIG. 20, for example.
With the above structure, the radio communication system shown in FIG. 18 operates in the following manner when implementing data communication such as personal computer communication between the personal computer 201 and the personal computer 207.
When data signals are transmitted from the personal computer 201 to the personal computer 207, digital data at 1200 bps outputted as communication data from the personal computer 201 are converted into analog signals in the modem 202, then outputted to the PHS terminal 203.
In the PHS terminal 203, the analog signals as the data signals from the modem 202 are conducted a PCM code modulation in the PCM processing unit 203b to be converted into data at 64 kbps, compressed into data at 32 kbps in the ADPCM processing unit 203c, then transmitted from the transmitting/receiving unit 203d to the PHS base station 204 over the radio line 208.
In the PHS base station 204, the data signals (time-division multiplexed signals) received from the PHS terminal 203 are demodulated in the transmitting/receiving unit 204a, demultiplexed in the time-division demultiplexing unit 204b, then converted into ADPCM data on four channels (at a transmission speed of 32 kbps) along with data on the other three channels.
After that, the data at 32 kbps inputted to the ADPCM unit 204c is expanded into PCM data at 64 kbps in synchronization with the ground network, then outputted to the switching system 205.
In the switching system 205, the PCM data at 64 kbps is switched in the switching unit 205a, converted into analog signals in the PCM processing unit 205b, then outputted to the modem 206.
Whereby, the analog signals inputted to the modem 206 are converted into digital data at 1200 bps and outputted to the personal computer 207.
When data signals are transmitted from the personal computer 207 to the personal computer 201, digital data at 1200 bps outputted as communication data from the personal computer 207 are converted into analog signals in the modem 206, then outputted to the switching system 205.
In the PCM processing unit 205b in the switching system 205, the analog data signals inputted from the modem 206 are converted into digital data at 64 kbps, switched in the switching unit 205a, then outputted to the PHS base station 204 as line signals on four channels along with another line signals not shown.
In the PHS base station 204, the inputted digital data at 64 kbps is compressed into ADPCM data at 32 kbps in the ADPCM processing unit 204c, multiplexed in a time-division fashion along with signals on the other three channels in the time division multiplexing/demultiplexing unit 204b, then transmitted from the transmitting/receiving unit 204a to the PHS terminal 203 over the radio line 208.
In the PHS terminal 203, the received data (at a transmission speed of 32 kbps) from the PHS base station 204 is expanded to data at 64 kbps in the ADPCM processing unit 203c, converted into analog signals in the PCM processing unit 203b, then outputted to the modem 202.
In the modem 202, the analog signals from the PCM terminal 203 are converted into digital signals at 1200 bps, outputted as data signals from the personal computer 207 to the personal computer 202, whereby personal computer communication is established.
Incidentally, when voice signals are received by the PHS terminal 203 in the case of normal voice communication using the communication modem shown in FIG. 18, the voice signals from the terminal apparatus not shown other than the PHS terminal 203 is received by the PHS terminal 203 via the switching system 205 and the PHS base station 204 over the radio line 208 similarly to the digital data from the PCM processing unit 205b in the switching system 205 in the case of the above personal computer communication. In the PHS terminal 203, analog signals amplified by the amplifying unit 203a are outputted to a speaker not shown so as to be regenerated.
When voice signals are transmitted from the PHS terminal 203, the voice signals which are analog signals inputted through a microphone not shown provided in the PHS terminal 203 are converted into digital voice signals at 32 kbps to be transmitted similarly to the analog signals from the modem 202 in the case of the above personal computer communication, then transmitted to a desired terminal apparatus via the PHS base station 204 and the switching system 205 similarly to the above data communication.
When data communication such as personal computer communication is implemented in the radio communication system as shown in FIG. 18, data outputted from the personal computers 201 and 207 are handled simultaneously with digitized voice data at 32 kbps on the radio line 208 although a transmission speed of the data from the personal computer 201 and 207 is 1200 bps.
More specifically, when a personal computer communication is implemented between the personal computer 201 and the personal computer 207, one communication channel is occupied by this personal computer communication. In consequence, although it is possible to transmit data at 32 kbits per one second, for example, the transmitted data is of 1200 bits as actual data. This means that the data communication is in a capacity thirty times an actual communication capacity, which leads to a low efficiency of utilization of the line.
As shown in FIG. 20, the control data transmitted and received over the control channel has less information quantity than the communication data. If transmitted at a transmission speed of 32 kbps, the control data is transmitted and received intermittently, which also leads to a low efficiency of utilization of the line.